U.S. Pat. No. 3,804,246, granted Apr. 16, 1974, to Karl Johan Ljungqvist, discusses known procedures for analizing wood chips used in making pulp, as to size and shape. It and the Swedish Pat. No. 304,395 discussed therein each discloses a popular form of sieve analysis trays and an available mechanism for shaking the trays. A disadvantage of the tray shaking mechanism disclosed by these patents is that the support links for the tray carrier occupy space about the stack of trays and make it somewhat difficult for the operator to load and unload the sieve trays. Also, the sieve trays disclosed by these patents are fixed to one another and to the support frame or carrier by a large number of screw type connectors, each of which requires separate handling.
U.S. Pat. No. 2,355,131, granted Aug. 8, 1944, to Delmar Kolleda discloses a sieve analysis mechanism adopted for conducting fines tests of Portland cements, oars, fertalizers, sands and other dry comminuted materials. The apparatus includes mechanism for shaking a stack of relatively small diameter sieve trays. The sieve trays are supported on a reciprocating carrier which sets on four spaced apart rollers. Coil springs are interconnected between corner regions of the carrier and adjacent portions of a frame which surrounds the carrier. Owing to this arrangement, operation of the device is such that the sifter mechanism is subject to both lateral movement and arcuate movement. The arcuate movement is of a compound character for the reason that the sifter is pivoted about a first support during one portion of the rotation of the drive crank and pivots about your second rollers support during another portion of the same rotation of the drive crank. The particular mechanism disclosed by this patent is relatively easy to load and unload because it is open about the tray carrier and it includes but two clamp down units for securing the stack of sieve trays to the carrier. However, it is not constructed to carry the weight of a plurality of sieve trays of the type used in sieve analysis of pulp chips and it is not adapted for causing horizontal rectilinear translation of the sieve trays.
The above three patents and the following additional United States Patents should be studied for the purpose of putting the present invention into proper perspective relative to the prior art:
U.S. Pat. No. 857,942, granted June 25, 1907, to William B. Howard; No. 1,141,727, granted June 1, 1915, to Alexander F. Seaman; No. 1,291,371, granted Jan. 14, 1919, to John W. Bell; No. 1,331,303, granted Feb. 17, 1920, to C. Wildhaber; No. 1,491,483, granted Apr. 1924, to Henry C. Cobb; No. 2,074,733, granted Mar. 23, 1937, to Donald C. Porter; No. 2,074,097, granted Mar. 30, 1937, to Harvey P. Dawrs and Henry R. Power; No. 2,358,453, granted Sept. 19, 1944, to Seth J. Gilson; No. 2,384,715, granted Sept. 11, 1945, to Royal V. Ward; No. 2,399,280, granted Apr. 30, 1946, to Hubert F. McDonell; No. 2,730,236, granted June 5, 1956, to Sam C. Aker; No. 3,098,037, granted July 15, 1963, to Robert A. Kline and Burl D. Tonjes; and No. 3,314,539, granted Apr. 18, 1967, to Earl R. Hitchman.